Repoman should check that the overlay in question defines a valid profiles/repo_name.
The emerge "missing repo_name" warning is enabled by default since this commit: http://git.overlays.gentoo.org/gitweb/?p=proj/portage.git;a=commit;h=60ce6cc9ad7b050d2cb6a66c84867bd5613a09a2 We could have repoman call the same function.
repoman support has been removed per bug 835013. Please file a new bug (or, I suppose, reopen this one) if you feel this check is still applicable to pkgcheck and doesn't already exist.